JAMB Physics 1981 past questions and answers

The ice and steam points of a mercury-in-glass thermometer of centigrade scale and of uniform bore correspond respectively to 3 cm and 19 cm lengths of the mercury thread. When the length is 12 cm, the temperature is

1. A.32°C
2. B.48°C
3. C.56°C
4. D.65°C
5. E.75°C

A vapour is said to be saturated when

1. A.more molecules return to the liquid than leave it
2. B.a dynamic equilibrium exists between the liquid molecules and the vapour molecules at a given temperature
3. C.the vapour pressure is atmospheric
4. D.the temparature of the vapour varies
5. E.all molecules are moving with the same speed.

The latent heat of fusion of a substance is the heat required to

1. A.raise the temperature of unit mass of the substance by 1°C
2. B.maintain unit mass of the substance at constant temperature
3. C.change unit mass of substance from solid to liquid at constant temperature
4. D.change unit mass of liquid to vapour at constant temperature
5. E.raise the temperature of unit mass by 100°C.

The following types of waves are all transverse EXCEPT

1. A.light waves
2. B.radio waves
3. C.sound waves
4. D.surface waves on water
5. E.x-rays.

The principle of the transmissibility of pressure in a fluid at rest in all directions is known as

1. A.Archimedes Principle
2. B.Flotation Principle
3. C.Newton's Law
4. D.Pascal's Law
5. E.Boyle's Law

When a fixed mass of an ideal gas expands at constant temperature, which property of the gas molecules increases?

1. A.Average number per unit volume
2. B.Average kinetic energy
3. C.Average speed
4. D.Average separation
5. E.Average number of collisions per unit time.

Which of the following does NOT describe the image formed by a plane mirror?

1. A.Erect
2. B.Laterally inverted
3. C.Same distance from mirror as object
4. D.Magnified
5. E.Virtual.

If a source of sound is moving, a stationary listener will hear a sound of different frequency. This is called

1. A.Doppler effect
2. B.resonance
3. C.ultra sound
4. D.diffraction of sound
5. E.rarefaction.

Which of the following elements are real magnetic materials?

1. A.Iron, steel and nickel
2. B.Copper, steel and iron
3. C.Lead, iron and brass
4. D.Glass, lead and steel
5. E.Stone, air and iron.

An inclined plane of angle θ, acting as a simple machine, has a velocity ratio

1. A.sin θ
2. B.1/sin θ
3. C.cos θ
4. D.1/cos θ
5. E.sin θ cos θ.

Heat may be transferred by conduction, convection and radiation. By which of these methods does heat travel through vacuum?

1. A.Conduction only
2. B.Convection only
3. C.Radiation only
4. D.All three methods
5. E.None of these methods.

Which of the following statements is applicable to a real image formed by a concave mirror? (i) It can be observed on a screen (ii) It is always inverted and in front of the mirror (iii) It only seems to exist (iv) It is formed by the actual converging of rays of light.

1. A.(i), (ii) and (iii) only
2. B.(i), (ii) and (iv) only
3. C.(i) and (iii) only
4. D.(i) and (ii) only
5. E.All four statements.

Which of the following is NOT an effect that can be produced by an electric current?

1. A.Heat
2. B.Light
3. C.Sound
4. D.Motion
5. E.None of the above.

A cell of e.m.f. 2 V and internal resistance 1 Ω supplies a current of 0.5 amps to a resistance whose value is

1. A.0.5 Ω
2. B.1 Ω
3. C.2 Ω
4. D.2.5 Ω
5. E.3 Ω

An example of a scalar quantity is

1. A.velocity
2. B.weight
3. C.electric charge
4. D.acceleration due to gravity
5. E.momentum.

When a ray of light passes from water to glass, it is

1. A.bent away from the normal
2. B.bent towards the normal
3. C.totally internally reflected
4. D.absorbed by the glass
5. E.broken into a pure spectrum.

The resistance of a 240 V, 60 watt electric filament bulb is

1. A.0.25 Ω
2. B.480 Ω
3. C.60 Ω
4. D.240 Ω
5. E.960 Ω

A body of mass 6 kg rests on an inclined plane. The normal reaction is R and the limiting frictional force is F as shown in the diagram (Fig. 1). If F is 30 N and g = 10 m s⁻², then the angle of inclination θ is

1. A.15°
2. B.30°
3. C.45°
4. D.60°
5. E.75°.

Two copper calorimeters O and P have identical dimensions but the outside of O is painted black while that of P is polished. The two are fitted with lids after equal volumes of boiling water have been added to them. They are then placed separately on a large metal table at a lower temperature. Several minutes later the temperature of

1. A.both will be equal but lower
2. B.P will be higher than that of O
3. C.O will be higher than that of P
4. D.O will be unchanged
5. E.P will be unchanged.

The effect of closing the key K in the circuit shown in Fig. 2 would be to

1. A.increase the current by 0.6 A
2. B.reduce the current by 0.6 A
3. C.reduce the current by 0.4 A
4. D.increase the current by 0.4 A
5. E.keep the current unchanged.

The wave motion shown (Fig. 3) has a frequency of

1. A.0.1 Hz
2. B.0.2 Hz
3. C.5 Hz
4. D.10 Hz
5. E.100 Hz

An aircraft travelled from Calabar to Kano as follows: It flew first to Ilorin covering a distance of 300 km, 30° West of North, and then flew 400 km, 60° East of North to Kano. What is the resultant displacement?

1. A.567 km
2. B.410 km
3. C.594 km
4. D.500 km
5. E.600 km

All of the following frequencies are overtones of 320 Hz EXCEPT

1. A.960 Hz
2. B.640 Hz
3. C.520 Hz
4. D.1280 Hz
5. E.1600 Hz

The driver in a motor car, of which the total mass is 800 kg and which is travelling at 20 m s⁻¹, suddenly observes a stationary dog in his path 50 m ahead. If the car brakes can exert a force of 2000 N, what will most likely happen?

1. A.The car will be able to stop immediately the driver notices the dog
2. B.The car will stop 30 m after hitting the dog
3. C.The car will stop 20 m in front of the dog
4. D.The driver will quickly reverse the car
5. E.The car will stop 5 m beyond the dog.

The absolute refractive indices of glass and water are 3/2 and 4/3 respectively. The refractive index at the interface when a ray travels from water to glass is

1. A.1/2
2. B.8/9
3. C.9/8
4. D.17/12
5. E.2

Which of the following statements is CORRECT?

1. A.Charges generated on glass rubbed with silk are called negative
2. B.Charges in various media can be carried by protons detached from their atoms.
3. C.The magnitude of any charge is a multiple of the charge of an electron
4. D.The intensity of an electric field is a scalar quantity
5. E.If 500 joules of work are required to move a 2-coulomb charge between two points, the potential difference between the two points is 100 V.

A mass of 2 kg on a surface (μ = ½) is connected to second mass of 4 kg over a frictionless pulley as shown in Fig. 4. If the acceleration due to gravity is 9.8 m s⁻² then the masses will

1. A.accelerate at 4.9 m s⁻²
2. B.remain stationary
3. C.accelerate at 9.8 m s⁻²
4. D.accelerate at 19.6 m s⁻²
5. E.Accelerate at 39.2 m s⁻².

Which type of radiation does NOT originate within the nucleus?

1. A.Alpha
2. B.Beta
3. C.Gamma
4. D.Neutron
5. E.X-rays.

The resistance of an open series circuit is

1. A.zero
2. B.half the normal resistance of the circuit
3. C.double the normal resistance of the circuit
4. D.one
5. E.infinite

The lack of power of accommodation which is mainly due to the hardening of the eye lens and is usual with the onset of old age is called

1. A.myopia
2. B.hypermetropia
3. C.presbyopia
4. D.astigmatism
5. E.eye ring.

When a lamp is placed on the axis and at various distances U from a converging lens, real images are formed at various distances V from the lens. Which of the graphs below will be obtained by plotting the values of quantity y (y = 1/V) against another quantity x (x = 1/U)?

1. A.A
2. B.B
3. C.C
4. D.D
5. E.E

A body falls freely under gravity (g = 9.8 m s⁻²) from a height of 40 m on to the top of a platform 0.8 m above the ground. Its velocity on reaching the platform is

1. A.784 m s⁻¹
2. B.80 m s⁻¹
3. C.78.4 m s⁻¹
4. D.39.2 m s⁻¹
5. E.27.7 m s⁻¹.

Alternating current can induce voltage because it has a

1. A.ripple value
2. B.varying magnetic field
3. C.weaker magnetic field than direct current
4. D.stronger magnetic field than direct current
5. E.high peak value

Two particles X and Y starting from rest cover the same distance. The acceleration of X is twice that of Y. The ratio of the time taken by X to that taken by Y is

1. A.1/2
2. B.2
3. C.1/√2
4. D.√2
5. E.4

A balloon inflated with helium gas at ground level is released. As it rises through a constant temperature atmosphere,

1. A.its pressure reduces but volume remains constant
2. B.the product of pressure and volume remains constant
3. C.both pressure and volume increase
4. D.its pressure remains constant but the volume decreases
5. E.both pressure and volume remain constant.

The quality (timbre) of sound depends on

1. A.amplitude
2. B.frequency
3. C.harmonics
4. D.velocity
5. E.wavelength

The mass of a proton is approximately equal to that of

1. A.an α-particle
2. B.a β-particle
3. C.a γ-ray
4. D.an electron
5. E.a neutron

An object placed on the principle axis of a convex lens of focal length 10 cm, produces a real image of double magnification. The image distance from the lens is

1. A.30 cm
2. B.25 cm
3. C.20 cm
4. D.15 cm
5. E.10 cm

A particle is under the action of three forces in equilibrium. Two of the forces are as shown in Fig. 5. The third force is

1. A.80 N along P
2. B.160 N at 60° to P
3. C.40√2 N at 45° to either P or Q
4. D.0 N
5. E.40√2 N at 30° to Q.

A liquid-in-glass thermometer should quickly register temperature changes. This is achieved by choosing a liquid that

1. A.is opaque
2. B.has high density
3. C.has regular expansion
4. D.has a high thermal conductivity
5. E.can wet glass

The extension in a spring when 5 g wt was hung from it was 0.56 cm. If Hooke's law is obeyed, what is the extension caused by a load of 20 g wt?

1. A.1.12 cm
2. B.2.14 cm
3. C.2.52 cm
4. D.2.80 cm
5. E.2.24 cm

In a light experiment with a convex lens a student plotted a graph, shown above (Fig. 6), of the reciprocal of object distance (1/U) against the reciprocal of the image distance (1/V). The focal length of the lens is given by

1. A.slope of the line PQ
2. B.reciprocal of either OP or OQ
3. C.length OP or OQ
4. D.area under the graph
5. E.ratio OP/OQ.

Which of the following is NOT directly associated with direct current (D.C.)?

1. A.A dry cell
2. B.A moving coil galvanometer
3. C.A transformer
4. D.A lead-acid accumulator
5. E.A commutator

The relationship between the period T and the length l of a simple pendulum is T = 2π(l/g)^1/2. From experimental data of T and l, one can obtain the following graphs. (i) T vs. l (ii) T vs. l² (iii) T² vs. l (iv) T vs. √l (v) log T vs. log l. Which of the graphs are linear?

1. A.All
2. B.Only (i) and (ii)
3. C.Only (iii) and (iv)
4. D.(iii), (iv) and (v)
5. E.None of them.

A transformer has 300 turns of wire in the primary coil and 30 turns in the secondary coil. If the input voltage is 100 volts, the output voltage is

1. A.5 volts
2. B.10 volts
3. C.15 volts
4. D.20 volts
5. E.25 volts

A closed coil of wire is placed near a magnet. The magnet lies along the axis of the coil. Under which of the following conditions would there be no current in the coil?

1. A.When the coil is moved towards the stationary magnet
2. B.When the coil is moved away from the stationary magnet
3. C.When the coil is held stationary but the magnet is moved towards the coil
4. D.When both the coil and the magnet are held stationary
5. E.When the coil is held stationary but the magnet is moved away from the coil.

If I is the current passing through a metallic resistor, and H is the rate of heat generated in the resistor at a constant temperature, then

1. A.H ∝ 1/I
2. B.H ∝ 1/I²
3. C.H ∝ √I
4. D.H ∝ I²
5. E.none of the above.

A solid weighs 4.8 g in air, 2.8 g in water and 3.2 g in kerosine. The ratio of density of the solid to that of the kerosine is

1. A.12
2. B.3
3. C.2
4. D.3/2
5. E.5/4